Focusing device comprising a plurality of scatterers and beam scanner and scope device

ABSTRACT

A focusing device includes a substrate and a plurality of scatterers provided at both sides of the substrate. The scatterers on the both sides of the focusing device may correct geometric aberration, and thus, a field of view (FOV) of the focusing device may be widened.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication 62/144,750, filed on Apr. 8, 2015, in the U.S. Patent andTrademark Office, and Korean Patent Application No. 10-2016-0014992,filed on Feb. 5, 2016, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in their entireties byreference.

This invention was made with government support under Grant No.W911NF-14-1-0345 awarded by the U.S. Army. The government has certainrights in the invention.

BACKGROUND

1. Field

Apparatuses and methods consistent with the present disclosure relate toa focusing device, and a beam scanner and a scope device that use thefocusing device as an optical path modifier.

2. Description of the Related Art

Optical sensors using semiconductor-based sensor arrays are widely usedin mobile devices, wearable devices, and the Internet of Things (IoT).Although size reduction of the aforementioned devices is desired, it isdifficult to reduce the thickness of focusing devices in theaforementioned devices.

Also, due to the increased use of 3-dimensional (3D) image sensors inthe IoT, gaming devices, and other mobile devices, focusing devices foradjusting a path of light incident on the 3D image sensors are required.However, the fields of view of the focusing devices may be limited bycoma aberration of the focusing devices. Thus, research has beenconducted to combine a plurality of optical lenses and thus remove comaaberration. However, since a substantial amount of space is necessary tocombine a plurality of optical lenses, it is difficult to reduce thesize of the focusing devices.

SUMMARY

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented exemplary embodiments.

According to an aspect of an exemplary embodiment, a focusing deviceincludes a substrate; a first thin lens provided at a first surface ofthe substrate and comprising a plurality of first scatterers; and asecond thin lens provided at a second surface of the substrate andcomprising a plurality of second scatterers. The first scatterers of thefirst thin lens are configured to correct geometric aberration (fieldcurvature, coma aberration, astigmatism, etc.) of the second thin lens.

The first and second thin lenses may be configured to allow light toform a focusing point on a focal plane regardless of an angle at whichlight is incident on the first surface.

A phase shift of light that passes through the second scatterers maydecrease from a central area of the second thin lens to a peripheralarea of the second thin lens.

A phase shift of light that passes through the first scatterers maydecrease from a peripheral area of the first thin lens to a middle areaof the first thin lens and increases again from the middle area of thefirst thin lens to a central area of the first thin lens.

The first and second thin lenses may be configured to change a locationat which light is focused on the focal plane according to the angle atwhich the light is incident on the first surface.

The first and second thin lenses area configured to determine thelocation at which the light may be focused on the focal plane accordingto Equation 1:h=f*tan θ

wherein ‘h’ is a distance between the location of the focusing point andan optical axis of the focusing device, ‘f’ is an effective focal lengthof the focusing device, and ‘θ’ is the incident angle of light.

Respective refractive indexes of the first and second scatterers may begreater than a refractive index of the substrate.

The substrate may include at least one selected from glass (fusedsilica, BK7, etc.), quartz, polymer (PMMA, SU-8, etc.) and plastic, andthe first and second scatterers comprise at least one selected fromcrystalline silicon (c-Si), polycrystalline silicon (poly Si), amorphoussilicon (a-Si), and group III-V compound semiconductors (GaP, GAN, GaAs,etc.), SiC, TiO₂, and SiN.

The first and second scatterers may be configured to allow incidentlight within a wavelength band to form a focusing point on a focalplane.

Distances between the first scatterers and distances between the secondscatterers may be less than wavelengths in the wavelength band.

Respective heights of the first scatterers and respective heights of thesecond scatterers may be less than wavelengths in the wavelength band.

The focusing device may further include an optical filter configured toblock the incident light of wavelengths of outside the wavelength band.

At least one of respective shapes of the first and second scatterers andrespective sizes of the first and second scatterers may change accordingto a thickness of the substrate.

Each of the first and second scatterers may have at least one of acylindrical shape, a cylindroid shape, and a polyhedral pillar shape.

According to another aspect of an exemplary embodiment, a beam scannerincludes an optical path modifier comprising a substrate, a first thinlens provided at a first surface of the substrate and comprising aplurality of first scatterers, and a second thin lens provided at asecond surface of the substrate and comprising a plurality of secondscatterers; and a light source array spaced apart from the secondsurface of the substrate and comprising a plurality of light sources.The first scatterers of the first thin lens are configured to correctcoma aberration of the second thin lens.

The optical path modifier may change path of light emitted from thelight sources according to respective locations of the light sources.

The optical path modifier may modify light emitted from one of the lightsources into parallel rays.

According to another aspect of an exemplary embodiment, a scope deviceincludes an object lens unit comprising a substrate; a first thin lensprovided at a first surface of the substrate and comprising a pluralityof first scatterers, and a second thin lens provided at a second surfaceof the substrate and comprising a plurality of second scatterers; and alight source facing the second surface of the substrate and configuredto emit light on a target object. The first scatterers of the first thinlens are configured to correct coma aberration of the second thin lens.

Light emitted by the light source may have at least two wavelengths withdifferent transmission rates with respect to the target object.

The light emitted by the light source may be scattered at differentlocations by the target object according to wavelengths of the lightemitted by the light source. The object lens unit may be configured tochange a path of the light according to the locations at which the lightis scattered by the target object.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the exemplary embodiments,taken in conjunction with the accompanying drawings in which:

FIG. 1 is a diagram of a focusing device according to a comparativeexample;

FIG. 2 is a diagram of an example in which light is obliquely incidentwith respect to an optical axis of the focusing device of FIG. 1;

FIGS. 3A to 3C are diagrams of light intensity distribution of a focalplane;

FIGS. 4A and 4B are diagrams of light intensity distribution on thefocal plane according to incident angles of light;

FIG. 5 is a focusing device according to an exemplary embodiment;

FIG. 6 is an exemplary diagram of a surface of a second thin lens;

FIGS. 7A to 7C are perspective views of various shapes of first andsecond scatterers;

FIG. 8A is a phase profile of a second thin lens;

FIG. 8B is a diagram of a phase profile of a first thin lens;

FIG. 9 is an exemplary diagram of a path of light incident on thefocusing device of FIG. 5;

FIGS. 10A and 10B are diagrams of light intensity distribution in asubstrate in the focusing device of FIG. 5;

FIGS. 11A to 11F are diagrams of light intensity distribution of animage formed on a focal plane by the focusing device of FIG. 5;

FIG. 12 is a graph of light intensity distribution of an image formed ona focal plane by the focusing device of FIG. 5;

FIG. 13 is an exemplary diagram of forming an image of an object by afocusing device;

FIG. 14 is a graph of a relationship between locations of focusingpoints and incident angles of light;

FIG. 15 is an exemplary diagram of an arrangement of first and secondscatterers;

FIGS. 16A to 16C are diagrams for describing changes in paths ofincident light according to wavelengths of the incident light;

FIGS. 17A to 17C are diagrams of light intensity distribution of animage formed on a focal plane by light incident in parallel to anoptical axis of a focusing device;

FIG. 18 is a diagram of changes in light intensity distribution of animage according to wavelengths and incident angles of incident light;

FIG. 19 is a diagram of a focusing device according to another exemplaryembodiment;

FIG. 20 is an imaging device according to another exemplary embodiment;

FIG. 21 is a diagram of a beam scanner according to an exemplaryembodiment;

FIG. 22 is a diagram of a scope device according to another exemplaryembodiment; and

FIG. 23 is an exemplary diagram of observing a target object by using ascope device.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. In this regard,the present exemplary embodiments may have different forms and shouldnot be construed as being limited to the descriptions set forth herein.Accordingly, the exemplary embodiments are merely described below, byreferring to the figures, to explain aspects. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings.

The terms used in the exemplary embodiments are selected as generalterms used currently as widely as possible considering the functions inthe present disclosure, but they may depend on the intentions of one ofordinary skill in the art, practice, the appearance of new technologies,etc. In specific cases, terms arbitrarily selected by the applicant arealso used, and in such cases, their meaning will be described in detail.Thus, it should be noted that the terms used in the specification shouldbe understood not based on their literal names but by their givendefinitions and descriptions through the specification.

Throughout the specification, it will also be understood that when anelement is referred to as being “connected to” another element, it canbe directly connected to the other element, or electrically connected tothe other element while intervening elements may also be present. Also,when a part “includes” or “comprises” an element, unless there is aparticular description contrary thereto, the part can further includeother elements, not excluding the other elements. In addition, the termssuch as “unit,” “-er (-or),” and “module” described in the specificationrefer to an element for performing at least one function or operation,and may be implemented in hardware, software, or the combination ofhardware and software.

The terms “configured of” or “includes” should not be construed asnecessarily including all elements or operations described in thespecification. It will be understood that some elements and someoperations may not be included, or additional elements or operations maybe further included.

While such terms as “first,” “second,” “A,” “B,” etc., may be used todescribe various components, such components must not be limited to theabove terms. The above terms are used only to distinguish one componentfrom another.

The present exemplary embodiments may have different forms and shouldnot be construed as being limited to the descriptions set forth herein.Elements and features that may be easily derived by one of ordinaryskill in the art to which the present disclosure pertains are within thespirit and scope of the present disclosure as defined by the appendedclaims. Hereinafter, the present exemplary embodiments will be describedwith reference to the accompanying drawings.

FIG. 1 is a diagram of a focusing device according to a comparativeexample.

Referring to FIG. 1, the focusing device according to the comparativeexample may include a substrate 10 and a plurality of scatterers 20provided at a side of the substrate 10. In the focusing device of FIG.1, a path of light exiting the substrate 10 may change as light passesthrough the plurality of scatterers 20. Shapes and materials of theplurality of scatterers 20 may vary according to functions performed bythe plurality of scatterers 20. For example, the plurality of scatterers20 of the focusing device of FIG. 1 may have a shape and a sizeappropriate for performing a function of a lens with positive refractivepower. Also, as shown in FIG. 1, the plurality of scatterers 20 mayallow light that is perpendicularly incident on the substrate 10 to forma focusing point at a focal plane S0.

FIG. 2 is a diagram of an example in which light is obliquely incidentwith respect to an optical axis (z-axis) of the focusing device of FIG.1;

Referring to FIG. 2, light incident in a direction that is not parallelto the optical axis of the focusing device may pass through theplurality of scatterers 20 but not focus on a single focusing point.Such phenomenon is referred to as geometric aberration. The geometricaberration may include coma aberration and field of curvatureaberration. The aforementioned geometric aberration may decreasesharpness of images formed by the focusing device. Also, the geometricaberration limits a field of view (FOV) of the focusing device.

FIGS. 3A to 3C are diagrams of light intensity distribution of a focalplane.

FIG. 3A shows light intensity distribution of an image formed by lightthat is parallel to the optical axis (z-axis) of the focusing device.FIG. 3B shows light intensity distribution of an image formed by lightincident at an incident angle of 1° with respect to the optical axis.FIG. 3C shows light intensity distribution of an image formed by lightincident at an incident angle of 3° with respect to the optical axis.Bars at a right hand side of FIGS. 3A to 3B indicates relative intensityof light.

Referring to FIG. 3A, when an incident angle of light is 0° (i.e., whenlight is parallel to the optical axis of the focusing device), an areawith high light intensity distribution may be narrow. That is, afocusing effect of the focusing device may be relatively excellent.Referring to FIG. 3B, when the incident angle of light is 1°, an areawith high intensity of light is wide. As the incident angle of lightincreases, the focusing effect of the focusing device may decrease.Referring to FIG. 3C, when the incident angle of light is 3°, intensityof light may decrease in a central area of the image. However,peripheral areas of the image may have greater intensity of light as theincident angle increases. That is, even when the incident angle of lightincreases by a small amount, the focusing effect of the focusing devicemay substantially decrease.

FIGS. 4A and 4B are diagrams of light intensity distribution on thefocal plane S0 according to incident angles of light.

Referring to FIG. 4A, as the incident angle of light increases, peaksmay be differently located in a graph of light intensity distribution.Also, as the incident angle increases, the graph of light intensitydistribution may be widened and peak values may decrease. Referring toFIG. 4B, when the incident angle is 3° or higher, peak values of thelight intensity distribution may decrease below more than half of peakvalues of when the incident angle is 0°. Also, a range of lightintensity distribution may substantially increase. When the incidentangle of light exceeds about 1°, image distortion due to coma aberrationmay increase.

FIG. 5 is a focusing device 100 according to an exemplary embodiment.

Referring to FIG. 5, the focusing device 100 according to an exemplaryembodiment may include a substrate 110, a first thin lens 120 includinga plurality of first scatterers 122 provided on a first surface S1 ofthe substrate 110, and a second thin lens 130 including a plurality ofsecond scatterers 132 provided on a second surface S2 of the substrate110.

The substrate 110 may be shaped as a plate. The first and secondsurfaces S1 and S2 of the substrate 110 may be substantially parallel toeach other. However, the first and second surfaces S1 and S2 do not haveto be completely parallel to each other but may be oblique with respectto each other. The substrate 110 may include a transparent material. Thetransparent material indicates a material with a high light transmissionrate. For example, the substrate 110 may include at least one selectedfrom glass (fused silica, BK7, etc.), quartz, polymer (PMMA, SU-8,etc.), and plastic.

The first thin lens 120 may include the plurality of first scatterers122 that are arranged on the first surface S1 of the substrate 110.Also, the second thin lens 130 may include the plurality of secondscatterers 132 that are arranged on the second surface S2 of thesubstrate 110. Unlike optical lenses of the related art, the first andsecond thin lenses 120 and 130 may change a path of light by using theplurality of first and the plurality of second scatterers 122 and 132.The plurality of first and the plurality of second scatterers 122 and132 may capture light incident near one another and resonate lightinside the plurality of first and the plurality of second scatterers 122and 132. The plurality of first and the plurality of second scatterers122 and 132 may adjust transmission and reflection properties of thelight incident on the plurality of first and the plurality of secondscatterers 122 and 132. For example, the plurality of first and theplurality of second scatterers 122 and 132 may modulate at least one ofan amplitude, phase, and polarization of transmitted light according tostructures and included materials of the plurality of first and theplurality of second scatterers 122 and 132. The plurality of first andthe plurality of second scatterers 122 and 132 may be arranged such thatdistribution of at least one of an amplitude, phase, and polarization ofthe transmitted light is modulated and thus a wavefront of thetransmitted light changes with respect to a wavefront of the incidentlight. Therefore, the plurality of first and the plurality of secondscatterers 122 and 132 may change a proceeding direction of thetransmitted light with respect to that of the incident light.

The second thin lens 130 may function as a lens with positive refractivepower. Shapes, sizes, materials, and an arrangement pattern of theplurality of second scatterers 132 may be modified so that the secondthin lens 130 has positive refractive power. Also, the plurality ofsecond scatterers 132 may be designed such that the second thin lens 130does not cause spherical aberration. To do so, the shapes, the sizes,the materials, and the arrangement of the plurality of second scatterers132 may vary according to a location on a surface of the substrate 110where the plurality of second scatterers 132 are arranged.

FIG. 6 is an exemplary diagram of a surface of the second thin lens 130.

Referring to FIG. 6, the plurality of second scatterers 132 may bearranged on the surface of the second thin lens 130. Waveform of lightthat passed through the second thin lens 130 may vary according toshapes, arrangement intervals, and an arrangement pattern of theplurality of second scatterers 132. When the plurality of secondscatterers 132 are arranged on the surface of the second thin lens 130as shown in FIG. 6, the second thin lens 130 may function as a lens withpositive refractive power.

The plurality of first scatterers 122 of the first thin lens 120 may bedesigned to correct coma aberration of the second thin lens 130. Shapes,materials, and arrangement pattern of the plurality of first scatterers122 may vary depending on a thickness of the substrate 110 and theshapes, the materials, and the arrangement pattern of the plurality ofsecond scatterers 132. In a general optical system, a plurality ofoptical lenses are combined to correct coma aberration of lenses.Therefore, the general optical system may be difficult to design andsize reduction may be difficult. However, the focusing device 100according to an exemplary embodiment may have the first and second thinlenses 120 and 130 on both surfaces of the substrate 110 by arrangingthe plurality of first and plurality of second scatterers 122 and 132 onthe both surfaces of the substrate 110. Accordingly, size reduction ofthe focusing device 100 may become convenient. Also, since the firstthin lens 120 may correct coma aberration of the second thin lens 130,the focusing device 100 may have a wide FOV.

FIGS. 7A to 7C are perspective views of various shapes of the individualscatterers of plurality of first and plurality of second scatterers 122and 132.

Referring to FIGS. 7A to 7C, the individual scatterers of the pluralityof first and the individual scatterers of the plurality of secondscatterers 122 and 132 in the first and second thin lenses 120 and 130may have a pillar structure. Such pillar structure may have any one ofcircular, oval, rectangular, and square cross-sections. FIG. 7A shows ascatterer shaped as a pillar with a circular cross-section. FIG. 7Bshows a scatterer shaped as a pillar with an oval cross-section. FIG. 7Cshows a scatterer shaped as a pillar with a quadrilateral cross-section.The pillar structure may be inclined at an angle in a height direction.

Although exemplary shapes of the plurality of first and the plurality ofsecond scatterers 122 and 132 are shown in FIGS. 7A to 7C, exemplaryembodiments are not limited thereto. For example, the plurality of firstand plurality of second scatterers 122 and 132 may be shaped aspolyhedral pillars or pillars with an L-shaped cross-section. The shapesof the plurality of first and plurality of second scatterers 122 and 132may be asymmetrical in a direction. For example, respectivecross-sections of the plurality of first and the plurality of secondscatterers 122 and 132 may be asymmetrical in a horizontal direction.Also, since the respective cross-sections of the plurality of first andthe plurality of second scatterers 122 and 132 may vary according torespective heights of the plurality of first and the plurality of secondscatterers 122 and 132, respective shapes of the plurality of first andthe plurality of second scatterers 122 and 132 may be asymmetrical withrespect to the respective heights thereof.

Respective refractive indexes of the plurality of first and theplurality of second scatterers 122 and 132 may be higher than arefractive index of the substrate 110. For example, the respectiverefractive indexes of the plurality of first and the plurality of secondscatterers 122 and 132 may be greater than the refractive index of thesubstrate 110 by approximately 1 or more. Therefore, the substrate 110may include a material with a relatively low refractive index, and theplurality of first and the plurality of second scatterers 122 and 132may include a material with a relatively high refractive index. Forexample, the plurality of first and the plurality of second scatterers122 and 132 may include at least one selected from crystalline silicon(c-Si), polycrystalline silicon (poly Si), amorphous silicon, Si₃N₄,GaP, GaAs, TiO₂, AlSb, AlAs, AlGaAs, AlGaInP, BP, and ZnGeP₂. Theplurality of first and the plurality of second scatterers 122 and 132may be additionally surrounded by materials with a low refractive index(SiO₂, polymer (PMMA, SU-8, etc.)) in upper and horizontal directions.

FIG. 8A is a phase profile of the second thin lens 130.

Referring to FIG. 8A, a phase shift of light incident on the second thinlens 130 may decrease from a central area of the second thin lens 130 toa peripheral area of the second thin lens 130. When the second thin lens130 is configured such that the phase profile shown in FIG. 8A issatisfied, the second thin lens 130 may function as a lens with positiverefractive power. Also, spherical aberration that occurs in generaloptical lenses may be decreased. The phase profile of the second thinlens 130 shown in FIG. 8A is merely exemplary, and exemplary embodimentsare not limited thereto. For example, a shape of the phase profile maybe changed according to a diameter, a focal length, etc. of the secondthin lens 130 changes.

Design conditions of the plurality of second scatterers 132 in thesecond thin lens 130 may be modified according to the phase profile ofthe second thin lens 130. For example, at least one of the shapes, thesizes, the materials, and the arrangement pattern of the plurality ofsecond scatterers 132 may be modified according to an arranged locationof the plurality of second scatterers 132 on the surface of thesubstrate 110. The shapes, the sizes, the materials, and the arrangementpattern of the plurality of second scatterers 132 may be determinedaccording to an amount of unwrapped phase shift of light that passesthrough the plurality of second scatterers 132. The amount of unwrappedphase shift indicates a phase component corresponding to a phase shiftvalue between 0 and 2π remaining after subtracting an integer multipleof 2π from an amount of phase shift. Respective structures and materialsof the plurality of first and the plurality of second scatterers 122 and132 may vary according to the amount of unwrapped phase shift of lightthat passes through the plurality of first and the plurality of secondscatterers 122 and 132.

FIG. 8B is a diagram of a phase profile of the first thin lens 120.

Referring to FIG. 8B, a phase shift of light incident on the first thinlens 120 may decrease from a peripheral area of the first thin lens 120to a middle area of the first thin lens 120 and then increase again fromthe middle area of the first thin lens 120 to a central area of thefirst thin lens 120. For example, as shown in FIG. 8B, the first thinlens 120 may have a phase profile in which the phase shift of theincident light decreases from the central area to a middle area having adiameter of approximately 150 μm and increases from the middle area tothe peripheral area. When the first thin lens 120 is configured suchthat the phase profile shown in FIG. 8B is satisfied, the first thinlens 120 may change a path of the incident light and thus correct comaaberration of the second thin lens 130. The phase profile of the firstthin lens 120 shown in FIG. 8B is merely exemplary, and exemplaryembodiments are not limited thereto. For example, a specific shape ofthe phase profile of the first thin lens 120 may be changed according toa diameter, a focal length, etc. of the first thin lens 120. Also, thespecific shape of the phase profile of the first thin lens 120 may bechanged according to the phase profile of the second thin lens 130 andthe thickness of the substrate 110.

FIG. 9 is an exemplary diagram of a path of light incident on thefocusing device 100 of FIG. 5.

Referring to FIG. 9, light may be incident on the focusing device 100 ina direction that is not parallel to the optical axis (z-axis) of thefocusing device 100. A path of light incident on the first thin lens 120may be changed by the plurality of first scatterers 122. After the pathis changed by the plurality of first scatterers 122, the light may passthrough the substrate 110, and the path of the light may be changedagain by the plurality of second scatterers 132. The first and secondthin lenses 120 and 130 may correct coma aberration of one another.Also, the first and second thin lenses 120 and 130 may allow the lightto form a focusing point on the focal plane S0 regardless of angles atwhich light is incident on the first surface S1 of the substrate 110.

FIGS. 10A and 10B are diagrams of light intensity distribution insidethe substrate 110 in the focusing device 100 of FIG. 5.

FIG. 10A shows an example in which light is incident in a directionparallel to an optical axis of the focusing device 100, and FIG. 10Bshows an example in which light is obliquely incident (at an incidentangle of 12°) with respect to the optical axis of the focusing device100. Referring to FIGS. 10A and 10B, light intensity distribution in thesubstrate 110 may vary according to an incident angle of light becausethe plurality of first scatterers 122 change a path of light thatproceeds into the substrate 110. Also, coma aberration of the focusingdevice 100 may be corrected by changing the light intensity distributionin the substrate 110.

FIGS. 11A to 11F are diagrams of light intensity distribution of animage formed on the focal plane S0 by the focusing device 100 of FIG. 5.

FIG. 11A shows light intensity distribution of an image formed by lightincident in parallel to an optical axis of the focusing device 100. FIG.11B shows light intensity distribution of an image formed by lightincident at an incident angle of 3°. FIG. 11C shows light intensitydistribution of an image formed by light incident at an incident angleof 6°. FIG. 11D shows light intensity distribution of an image formed bylight incident at an incident angle of 9°. FIG. 11E shows lightintensity distribution of an image formed by light incident at anincident angle of 12°. FIG. 11F shows light intensity distribution of animage formed by light incident at an incident angle of 15°. Bars at aright hand side of FIGS. 11A to 11F indicates intensity of light.

Referring to FIGS. 11A to 11F, a location of a focusing point may changeas an incident angle of light changes from 0° to 15°. However, a shapeof light intensity distribution may nearly not change at the location ofthe focusing point. By using the focusing device 100 of FIG. 5,intensity of light at the focusing point may be almost maintained at asteady rate even when the incident angle of light changes. Also, unlikeFIGS. 3A to 3C, the focusing device 100 of FIG. 5 may prevent defocusingeven when the incident angle of light increases.

FIG. 12 is a graph of light intensity distribution of an image formed onthe focal plane S0 by the focusing device 100 of FIG. 5.

Referring to FIG. 12, a location of a focusing point may change as anincident angle changes from 0° to 15°. However, a shape and a peak oflight intensity distribution graph may almost not change at the locationof the focusing point. Also, unlike FIGS. 4A and 4B, the graph may showonly one peak instead of a plurality of peaks even when the incidentangle of light increases. As shown in FIG. 12, coma aberration of thefocusing device 100 may be corrected. Therefore, even when the incidentangle of light changes, the shape of the light intensity distributionmay almost not change at the focusing point. Also, the focusing device100 may have a wide FOV.

FIG. 13 is an exemplary diagram of forming an image of an object by thefocusing device 100.

For convenience, the focusing device 100 and an image are enlarged inFIG. 13 and are not drawn to scale. However, an actual distance betweenan object and the focusing device 100 and a size of the object may besubstantially different from a height of the focusing device 100.Therefore, when light reflected from a point of the object is incidenton the focusing device 100, the light may be substantially parallelrays. Referring to FIG. 13, a distance h between a location of afocusing point and an optical axis of the focusing device 100 may varyaccording to an angle θ at which light is incident. For example, whenthe focusing device 100 is designed such that image distortion is notcreated, the distance h between the location of the focusing point andthe optical axis of the focusing device 100 may satisfy Equation 1.h=f*tan θ  [Equation 1]

In Equation 1, ‘h’ is the distance between the location of the focusingpoint and the optical axis of the focusing device 100, ‘f’ is aneffective focal length of the focusing device 100, and ‘θ’ is anincident angle of light.

As another example, when the focusing device 100 is provided as anorthographic fisheye lens to enlarge the FOV of the focusing device 100,the distance h between the location of the focusing point and theoptical axis of the focusing device 100 may satisfy Equation 2h=f*sin θ  [Equation 2]

In Equation 2, ‘h’ is the distance h between the location of thefocusing point and the optical axis of the focusing device 100, ‘f’ isan effective focal length of the focusing device 100, and ‘θ’ is anincident angle of light.

FIG. 14 is a graph of a relationship between locations of focusingpoints and incident angles of light.

In FIG. 14, a solid line indicates the focusing device 100 forming adistortion free image, and a dashed line indicates the focusing device100 provided as an orthographic fisheye lens. A location at which animage is formed according to incident angles of light may be changed bymodifying designs of the plurality of first and the plurality of secondscatterers 122 and 132. Accordingly, an image distortion degree and theFOV of the focusing device 100 may be adjusted. For example, when imageaccuracy is required, an image formed by light that passed through thefocusing device 100 may be determined according to the solid line ofFIG. 14. As another example, a wide FOV is required, an image formed bylight that passed through the focusing device 100 may be determinedaccording to the dashed line of FIG. 14.

The focusing device 100 of FIG. 5 may focus incident light according towavelengths of incident light.

The first and second thin lenses 120 and 130 may differently change adirection of incident light according to wavelengths of the incidentlight. Therefore, the focusing device 100 according to an exemplaryembodiment may only allow incident light within a certain wavelengthband to form a focusing point on the focal plane S0. Also, the first andsecond thin lenses 120 and 130 may differently correct coma aberrationaccording to the wavelengths of the incident light. A wavelength oflight that is allowed by the focusing device 100 to form the focusingpoint on the focal plane S0 is a design wavelength of the focusingdevice 100. Design conditions of the plurality of first and theplurality of second scatterers 122 and 132 may vary according to thewavelength of light that is to be focused by the focusing device 100,i.e., the design wavelength of the focusing device 100.

FIG. 15 is an exemplary diagram of an arrangement of the plurality offirst and the plurality of second scatterers 122 and 132.

Referring to FIG. 15, intervals T between the plurality of first and theplurality of second scatterers 122 and 132, respective heights h of theplurality of first and the plurality of second scatterers 122 and 132,and an arrangement pattern of the plurality of first and the pluralityof second scatterers 122 and 132 may be determined according to thedesign wavelength of the focusing device 100. The intervals T betweenthe plurality of first and the plurality of second scatterers 122 and132 may be less than the design wavelength. For example, the intervalsbetween the plurality of first and the plurality of second scatterers122 and 132 may be equal to or less than ¾ or ⅔ of the designwavelength. Also, the respective heights h of the plurality of first andthe plurality of second scatterers 122 and 132 may be less than thedesign wavelength. For example, the respective heights h of theplurality of first and the plurality of second scatterers 122 and 132may be equal to or less than ⅔ of the design wavelength.

FIGS. 16A to 16C are diagrams for describing changes in path of incidentlight according to wavelengths of the incident light. The focusingdevice 100 of FIGS. 16A to 16C are designed to be appropriate forfocusing about light having a wavelength of 850 nm.

Referring to FIG. 16A, when light having a wavelength that correspondsto the design wavelength of the focusing device 100 is incident, afocusing point of the light may be formed on the focal plane S0regardless of an incident angle of the light. However, referring to FIG.16B, when light having a wavelength (830 nm) that is less than thedesign wavelength is incident, the light may reach the focal plane S0before a focusing point of the light is formed. Also, referring to FIG.16C, when light having a wavelength (870 nm) that is greater than thedesign wavelength is incident, a focusing point may be formed before thelight reaches the focal plane S0.

FIGS. 17A to 17C are diagrams of light intensity distribution of animage formed on the focal plane S0 by light incident in parallel to anoptical axis of the focusing device 100.

Referring to FIG. 17B, an image formed by light having a wavelength (850nm) corresponding to the design wavelength of the focusing device 100may have narrow light intensity distribution. However, referring toFIGS. 17A and 17C, an image formed by light having a wavelength (830 nmor 870 nm) different from the design wavelength of the focusing device100 may have wide light intensity distribution. That is, when thewavelength of incident light is different from the design wavelength ofthe focusing device 100, a focusing effect of the light incident inparallel to the optical axis of the focusing device 100 may decrease.

FIG. 18 is a diagram of changes in light intensity distribution of animage according to wavelengths and incident angles of incident light.

Referring to FIG. 18, when a wavelength of incident light corresponds toa design wavelength (850 nm), a focusing effect may not decrease untilan incident angle reaches 20°. Also, when the incident angle is equal to40°, light intensity distribution may change by a minor degree. However,when light has a wavelength of 810 nm, there may be a significant changein light intensity distribution as an incident angle changes to 20°.Also, when light has a wavelength of 870 nm, there may be a significantchange in light intensity distribution as an incident angle changes to40°. That is, when the wavelength of incident light is different fromthe design wavelength of the focusing device 100, the focusing device100 may be less effective in correcting coma aberration.

FIG. 19 is a diagram of a focusing device 100 according to anotherexemplary embodiment.

Referring to FIG. 19, the focusing device 100 may include an opticalfilter 160 that blocks wavelengths of the incident light which aredifferent from the design wavelength of the focusing device 100. Theoptical filter 160 may transmit light having a wavelength equal orsimilar to the design wavelength of the focusing device 100 from theincident light. Also, the optical filter 160 may reflect or absorb lighthaving a wavelength that is not similar to the design wavelength. Theoptical filter 160 may filter the wavelength of incident light and thusprevent a light component with a weak focusing effect from reaching afocal plane S0.

FIG. 20 is an imaging device according to another exemplary embodiment.

Referring to FIG. 20, the imaging device may include the focusing device100 of FIG. 5, and an optical detector 140 that detects light thatpassed through the focusing device 100. The optical detector 140 mayinclude an optical detection layer 144 provided at the focal plane S0 ofthe focusing device 100 and a cover glass 142 that protects the opticaldetection layer 144 and the optical detection layer 144. The opticaldetection layer 144 may include a plurality of charge-coupled devices(CCDs), complementary metal-oxide semiconductor (CMOS) sensors, photodiodes, etc. The optical detection layer 144 may convert optical signalsincident on the optical detection layer 144 into electric signals.

FIG. 21 is a diagram of a beam scanner 200 according to an exemplaryembodiment.

Referring to FIG. 21, the beam scanner 200 may include the focusingdevice 100 of FIG. 5. Also, the beam scanner 200 may include a lightsource array 220 that includes a plurality of light sources 222. Thelight source array 220 may be provided at a location of the focal planeS0 of the focusing device 100 of FIG. 5. Therefore, a distance betweenthe light source array 220 and the focusing device 100 may varyaccording to an effective focal length of the focusing device 100.

The focusing device 100 may focus incident light to another locationaccording to an incident angle of the light incident on the firstsurface S1 of the substrate 110. Similarly, a path of light that passedthrough the focusing device 100 may change depending on respectivelocations of the plurality of light sources 222 emitting light from thelight source array 220 facing the second surface S2 of the substrate110. For example, as shown in FIG. 21, paths of light rays L1 and lightrays L2 that passed through the focusing device 100 may change accordingto the respective locations of the plurality of light sources 222emitting light. Also, the light rays L1 and L2 that passed through thefocusing device 100 may be parallel rays. Therefore, the focusing device100 may function as an optical path modifier of the beam scanner 200.

Since the first and second thin lenses 120 and 130 are designed tocorrect coma aberration of each other, the focusing device 100 may havea wide FOV. Accordingly, an area of the light source array 220 may beless limited. Also, the light source array 220 may adjust the respectivelocations of the plurality of light sources 222 and thus easily adjustdirection of light emitted by the beam scanner 200.

FIG. 22 is a diagram of a scope device 300 according to anotherexemplary embodiment. Referring to FIG. 22, the scope device 300 mayinclude a focusing device 100, and a light source 310 arranged to face asecond surface S2 of a substrate 110 of the focusing device 100 andemitting light on a target object 10. Light emitted from the lightsource 310 may pass through the target object 10 and be incident on thefocusing device 100. Also, since the focusing device 100 may function asa focusing lens, the focusing device 100 may be used as an object lensof the scope device 300. In this case, the scope device 300 refers to adevice for observing objects that are small or far away, such as amicroscope or a telescope. Since the focusing device 100 has a wide FOV,the scope device 300 may observe a large area of the target object 10without coma aberration.

FIG. 23 is an exemplary diagram of 3-dimensional (3D) volumetric imaginga target object 20 by using the scope device 300.

Referring to FIG. 23, when the light source 310 emits light havingvarious wavelengths on the target object 20, the focusing device 100 ofthe scope device 300 may function as an object lens that has differentfocal lengths with respect to the target object 20 according to thewavelengths of the light emitted from the light source 310. The lightsource 310 may emit light having different wavelengths on the targetobject 20 according to time variation. Alternatively, the light source310 may simultaneously emit light having different wavelengths on thetarget object 20. The scope device 300 may divide light that passedthrough the target object 20 according to its wavelengths and recordimages of the target object 20. Also, the scope device 300 may analyzethe images according to the wavelengths of light, and thus extract a 3Dimage including depth information of the target object 20.

It should be understood that exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exemplaryembodiment should typically be considered as available for other similarfeatures or aspects in other exemplary embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. A focusing device comprising: a substrate; afirst thin lens provided at a first surface of the substrate andcomprising a plurality of first scatterers; and a second thin lensprovided at a second surface of the substrate and comprising a pluralityof second scatterers, wherein the plurality of first scatterers of thefirst thin lens are configured to correct geometric aberration of thesecond thin lens.
 2. The focusing device of claim 1, wherein the firstand the second thin lenses are configured to allow light to form afocusing point on a focal plane.
 3. The focusing device of claim 1,wherein a phase shift of light that passes through the plurality ofsecond scatterers decreases from a central area of the second thin lensto a peripheral area of the second thin lens.
 4. The focusing device ofclaim 3, wherein a phase shift of light that passes through theplurality of first scatterers decreases from a peripheral area of thefirst thin lens to a middle area of the first thin lens and increasesfrom the middle area of the first thin lens to a central area of thefirst thin lens.
 5. The focusing device of claim 2, wherein the firstand the second thin lenses are configured to change a location of thefocusing point according to an angle at which the light is incident onthe first surface.
 6. The focusing device of claim 5, wherein the firstand the second thin lenses area configured to determine the location ofthe focusing point according to Equation 1:h=f*tan θ wherein ‘h’ is a distance between the location of the focusingpoint and an optical axis of the focusing device, ‘f’ is an effectivefocal length of the focusing device, and ‘θ’ is an angle at which thelight is incident on the first surface.
 7. The focusing device of claim1, wherein respective refractive indexes of the first and the secondscatterers are greater than a refractive index of the substrate by atleast
 1. 8. The focusing device of claim 7, wherein the substratecomprises at least one selected from fused silica, BK7, quartz,polymethyl methacrylate (PMMA), SU-8, and plastic, and the first andsecond scatterers comprise at least one selected from crystallinesilicon (c-Si), polycrystalline silicon (poly Si), amorphous silicon(a-Si), Si₃N₄, GaP, GaAs, TiO₂, AlSb, AlAs, AlGaAs, AlGaInP, BP, andZnGeP₂.
 9. The focusing device of claim 1, wherein the plurality offirst and the plurality of second scatterers are configured to allowincident light within a wavelength band to form a focusing point on afocal plane.
 10. The focusing device of claim 9, wherein distancesbetween the plurality of first scatterers and distances between theplurality of second scatterers are less than wavelengths in thewavelength band.
 11. The focusing device of claim 9, wherein respectiveheights of the plurality of first scatterers and respective heights ofthe plurality of second scatterers are less than wavelengths in thewavelength band.
 12. The focusing device of claim 9, further comprisingan optical filter configured to block the incident light of wavelengthsoutside the wavelength band.
 13. The focusing device of claim 1, whereinat least one of respective shapes of the plurality of first and theplurality of second scatterers and respective sizes of the plurality offirst and the plurality of second scatterers changes according to athickness of the substrate.
 14. The focusing device of claim 1, whereineach of the plurality of first and the plurality of second scatterershas at least one of a cylindrical shape, an cylindroid shape, and apolyhedral pillar shape.
 15. A beam scanner comprising: an optical pathmodifier comprising a substrate, a first thin lens provided at a firstsurface of the substrate and comprising a plurality of first scatterers,and a second thin lens provided at a second surface of the substrate andcomprising a plurality of second scatterers; and a light source arrayspaced apart from the second surface of the substrate and comprising aplurality of light sources, wherein the plurality of first scatterers ofthe first thin lens are configured to correct coma aberration of thesecond thin lens.
 16. The beam scanner of claim 15, wherein the opticalpath modifier changes a path of light emitted from the plurality oflight sources according to respective locations of the light sources.17. The beam scanner of claim 15, wherein the optical path modifiermodifies light emitted from one of the plurality of light sources intoparallel rays.
 18. A scope device comprising: an object lens unitcomprising a substrate; a first thin lens provided at a first surface ofthe substrate and comprising a plurality of first scatterers, and asecond thin lens provided at a second surface of the substrate andcomprising a plurality of second scatterers; and a light source facingthe second surface of the substrate and configured to emit light on atarget object, wherein the plurality of first scatterers of the firstthin lens are configured to correct coma aberration of the second thinlens.
 19. The scope device of 18, wherein light emitted by the lightsource has at least two wavelengths with different transmission rateswith respect to the target object.
 20. The scope device of claim 19,wherein the light emitted by the light source is scattered at differentlocations by the target object according to wavelengths of the lightemitted by the light source, and the object lens unit is configured tochange a path of the light according to the locations at which the lightis scattered by the target object.